Field of the Invention
The invention relates to an optical apparatus.
Description of Related Art
In general optical apparatuses, optical components are used to influence the light. For example, optical components may be used to reflect light, refract light, diffract light, form light interference, diffuse light, filter light, polarize light, transmit light, block light, and so on. Some optical components are made of optical plastics. Generally, optical plastics have low thermal conductivity and high linear coefficient of thermal expansion. As a result, when an optical component made of optical plastics is reduced to comply with the reduction of an optical apparatus, the density of light energy impinging on the optical component is increased so that the optical component absorbs more light energy, the temperature thereof is thus increased more, and the deformation thereof is increased more. When the optical component deforms, the optical quality of the optical component is reduced.
On the other hand, when the density of light energy impinging on different parts of the optical component is different, the temperature distribution of the optical component is not uniform, and the lower the thermal conductivity, the less uniform the temperature distribution of the optical component. As a result, the deformation of the optical component is not uniform or symmetrical, which reduces the optical quality of the optical component greatly.
Besides, when the optical apparatus is used in an environment with a great temperature variation, e.g. from 25° C. to 40° C., the deformation of the optical component at different temperature is different, so that the reliability of the optical apparatus is reduced.